How i fix it. please help me.

[AnuchitO]

Given I send and accept JSON          # cucumber-api-steps-0.13/lib/cucumber/api_steps.rb:21
      undefined local variable or method `app' for #<Object:0x007ffc32d779f0> (NameError)

[AnuchitO]

After i setup project cucumber when i run

cucumber -p verbose features/

and then i found it. i don't know to fix it. please help.